Gas temperature control for a plasma process

ABSTRACT

A method and system for controlling the temperatures of at least one gas in a plasma processing environment prior to the at least one gas entering a process chamber. This temperature control may vary at different spatial regions of a showerhead assembly (either an individual gas species or mixed gas species). According to one embodiment, an in-line heat exchanger alters (i.e., increases or decreases) the temperature of passing gas species (either high- or low-density) prior to entering a process chamber, temperature change of the gases is measured by determining a temperature of the gas both upon entrance into the in-line heat exchanger assembly and upon exit.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser.No. 60/299,725, filed Jun. 22, 2001, the contents of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to a method and system for controllinga gas temperature in a plasma processing environment.

2. Discussion of the Background

Plasma reactors are being constructed with increasingly tight processcontrols. Plasma processes involve dissociating the molecules in the gaswithin the process chamber using an RF electric field. Dissociationwithin the plasma creates positively charged ions, free electrons, andneutrals. These particles interact with the wafer and with each other.These interactions are governed by chemical principles. One dominantfactor governing these reactions is temperature. Temperature controlsystems exist to regulate the temperature of wafers when they are on awafer chuck in a reactor being etched.

U.S. Pat. No. 5,653,808, entitled “Gas injection system for CVDreactors,” describes a CVD reactor that includes separate reaction andpressure chambers, where the reaction chamber is contained within andisolates reactant gases from the pressure chamber. The reactor alsoincludes a gas injection system that injects process gas(es) (e.g.,hydrogen) into the reaction chamber in a somewhat vertical directionthrough a bottom surface of the reaction chamber.

The flow of the gas is intermediate the flow of the process gas(es) anda surface of the reaction chamber, thereby re-directing the process gasflow parallel to the top surface of a wafer therein. In this manner, thereaction chamber does not require a long entry length for the processgas(es).

U.S. Pat. No. 5,911,834, entitled “Gas delivery system” and assigned toApplied Materials Inc. (Santa Clara, Calif.), describes a method andapparatus for delivering at least one process gas and at least onecleaning gas into at least one processing region. The gas distributionsystem includes a gas inlet and a gas conduit, each disposed to deliverat least one gas into the chamber via a desired diffusing passage. Also,a gas delivery method and apparatus for splitting a gas feed intomultiple feed lines is provided having a gas filter disposed upstreamfrom a splitting coupling disposed in the line.

U.S. Pat. No. 6,030,456, entitled “Installation to supply gas” andassigned to Winbond Electronics Corp. (Hsinchu, TW), describes anadjustable gas supply in a reaction chamber according to the conditionsin the reaction chamber. The installation comprises sensors, agas-supplying panel and a driving device. The sensors are located in thereaction chamber to sense the conditions in the reaction chamber. Thegas-supplying panel has a plurality of asymmetrically located aperturesand gas is supplied through these apertures. The driving device, coupledto the sensors and the gas-supplying panel, drives the gas-supplyingpanel to respond to the conditions sensed by the sensors, in which thegas-supplying panel can adjust the positions of the gas supplied throughthe apertures.

U.S. Pat. No. 6,068,703, entitled “Gas mixing apparatus and method” andassigned to Applied Materials, Inc. (Santa Clara, Calif.), describesapparatuses, systems, and methods related to the manufacture ofintegrated circuits. Specifically, embodiments include apparatusdesigned to provide mixture for gases used in a semiconductor processingsystem. In one embodiment, the gas mixing apparatus includes a gas mixerhousing having a gas inlet, a fluid flow channel, and a gas outlet. Thefluid flow channel is fluidly coupled to a plurality of gas sources. Themajority of the gas mixture occurs in the fluid flow channel whichincludes one or more fluid separators for separating the gas into pluralgas portions and one or more fluid collectors for allowing the pluralgas portions to collide with each other to mix the gas portions.

U.S. Pat. No. 6,071,349, entitled “Gas supplying apparatus andvapor-phase growth plant” and assigned to Shin-Etsu Handotai Co. Ltd.(Tokyo, JP), describes a vapor-phase growth plant which has a dopant gassupplying apparatus including plural dopant gas supplying containers,and a multiple stage gas flow subsystem with plural dopant gas supplyconduits therein. The dopant gas supply conduits form a tournament-stylenetwork with a plurality of confluences on which the dopant gas supplyconduits are united and the gas flows therein are merged for subjectionto mixing which results in a decreasing number of dopant gas supplyconduits as the dopant gas flows proceed in the multiple stage gas flowsubsystem.

The above discussed patents solve some temperature related problems,however, the temperatures of gases entering the process chamber duringthe etching process are not controlled.

SUMMARY OF THE INVENTION

It is an object of the present invention to extend the range of etchingprocess recipes by providing control of the temperatures of the gases.Generally the present invention is directed to a method of controllingthe temperature of at least one gas prior to the gas entering a processchamber. Temperature controllers can also be used to vary gastemperatures at different spatial regions of a showerhead assembly(either an individual gas species or mixed gas species).

According to one embodiment, an in-line heat exchanger alters (i.e.,increases or decreases) the temperature of passing gas species (eitherhigh- or low-density) prior to entering a process chamber, temperaturechange of the gases is measured by determining a temperature of the gasboth upon entrance into the in-line heat exchanger assembly and uponexit. This enables tracking of the operation of the system configurationby a gas temperature control system and prediction of what will happenin the process chamber. Depending on the desired reactant gas mixture,gas species can be heated or cooled to different temperatures beforebeing mixed and subsequently dispersed into a process chamber.

In at least one embodiment, the present invention increases at least oneperformance characteristic (e.g., etch rate, uniformity, selectivity,ease of chamber cleaning, and various plasma properties).

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the present invention and many of theattendant advantages thereof will become readily apparent with referenceto the following detailed description, particularly when considered inconjunction with the accompanying drawings, in which:

FIG. 1 is a schematic illustration of a plasma processing system withgas temperature control according to a first embodiment;

FIG. 2 is a schematic illustration of a plasma processing system withgas temperature control according to a second embodiment;

FIG. 3 is a schematic illustration of a plasma processing system withgas temperature control according to a third embodiment;

FIG. 4 is a schematic illustration of a plasma processing system withgas temperature control according to a fourth embodiment;

FIG. 5 is a side cross section of a temperature controller;

FIG. 6 is a cross section of the diameter of the temperature controllerof FIG. 5; and

FIG. 7 is a flowchart illustrating temperature regulation according tothe present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, wherein like reference numerals designateidentical or corresponding parts throughout the several views, FIG. 1shows a first gas temperature-control embodiment 100 that includes firstgas line 110 ₁, second gas line 110 ₂, third gas line 110 ₃, and nth gasline 110 _(n), temperature controller (T/C) 130, process chamber 190(e.g., a conventional plasma-etching chamber), showerhead 140, chamberwall 150, chuck 160, pump port 170, and bellows 180.

Gases 120 ₁, through 120 ₂, are gases used to process wafers. Examplesof such gases include HBr, SF₆ or Cl₂ diluted with Ar for silicon etch;C₄F₈, C₅F₈ or CF₄ diluted with Ar for oxide (e.g., SiO₂ etch); SiH₄ orSiCl₂H₂, and CO₂ and H₂O, or N₂O for oxide (e.g., SiO₂) deposition;Si(OC₂H₅) for oxide deposition; BCl₃, Cl₂, SF₆, CF₄, CFCl₃, CF₂Cl₂,CF₃Cl, CHF₃ or C₂ClF₅ for metal etch; NH₃, N₂, AsH₃, B₂H₆, KCl PH₃, WF₆and SiH₄ for chemical vapor deposition (CVD) applications; or O₂ forashing (resist removal) processes. A typical set of gases employed foroxide etching includes Ar, C₄F₈, (CO) and O₂.

Gas lines 110 ₁ through 110 _(n), are channels, preferably constructedof metal (e.g., single or double-wall stainless steel tubing) throughwhich gases 120 ₁ through 120 _(n) travel before combining in neck 125.Neck 125 serves to homogeneously mix gases prior to entering processchamber 190.

The system further includes temperature controller 130 and showerhead140. Temperature controller 130 preferably is capable of both raisingand lowering the temperature of gas passing through it, not only topreset constant levels, but also in response to dynamic and time varyingtemperature trajectories. An exemplary temperature controller 130 isdisclosed in additional detail in FIGS. 5 and 6. As illustrated in FIG.1, showerhead 140 comprises a plate that includes a plurality of gasinjection holes spaced in such a manner as to allow a controlleddistribution of process gas introduction to the process chamber 190above the wafer.

Chamber wall 150 is the wall of the process chamber 190 that serves tocontain a vacuum that supports formation of a plasma during deviceprocessing. Chamber walls are generally fabricated from aluminum andeither anodized, spray coated with a protective coating such as Y₂O₃ orclad with protective chamber liners (e.g., silicon, quartz, siliconcarbide, boron carbide and alumina) in order to avoid direct contactbetween the (aluminum) chamber walls and the plasma.

Chuck 160 serves to hold and clamp a substrate (e.g., a liquid crystaldisplay or a wafer of semiconductor material), and also serves toconfine a thin layer of helium gas to drain heat from the substrateduring plasma-etch fabrication steps. The clamping force can be appliedto the substrate via an electrostatic clamp electrode embedded withinthe chuck and biased to attract the substrate to the chuck 160. Gas(e.g., Helium) is supplied to the backside of the substrate in order toimprove the thermal contact between the substrate backside and the chuckupper surface.

Pump port 170 is a passageway through which gases are purged from theprocess chamber 190. Pump port 170 is preferably attached to a vacuumpump (e.g., a turbo-molecular vacuum pump (TMP) capable of pumping speedin excess of 5000 liters per second). In conventional plasma processingdevices utilized for dry plasma etch, a 1000 to 3000 liter per secondTMP is employed. TMPs are useful for low pressure processing, typicallyless than 50 mTorr. At higher pressures, the TMP pumping speed falls offdramatically. For high pressure processing (i.e., greater than 100mTorr), a mechanical booster pump and dry roughing pump is recommended.

Bellows 180 is a circular, compressible metal element. Prefabricatedbellows are well known to the industry and are commonly available fromsuppliers such as Senior Flexonics, Inc., Metal Bellows Division (536Sandy Oaks Boulevard, Ormond Beach, Fla. 32174). An exemplary bellowsuitable for a chuck useful in 200 mm substrate processing might beModel number DD-01-00001-83.

The elements of FIG. 1 are interconnected as follows. For each i, where1≦i≦n, gas 120 _(i) is supplied to gas line 110 _(i) (e.g., gas 120 ₁ issupplied to first gas line 110 ₁), each through an independent mass flowcontroller. The n gas lines combine at neck 125. Neck 125 extendsbetween the confluence of the plurality of gas lines and the showerhead140 included in process chamber 190. Process chamber 190 is enclosed bychamber wall 150 and further includes chuck 160 and bellows 180. Pumpport 170 is attached to chamber wall 150. T/C 130 is located along neck125.

In operation, a production substrate (not shown) is placed on chuck 160within process chamber 190 such that the surface of the substrate to beetched (or to which material is deposited) faces the showerhead 140. Thesubstrate etching process takes place according to a process recipeselected for the substrate. The substrate is heated or cooled to aprescribed process temperature. In accordance with flow rates given bythe process recipe, gases 120 ₁ through 120 _(n) flow through gas lines110 ₁ through 110 _(n), combine in neck 125 and flow through T/C 130where their combined temperature is changed. The combined gases continuealong neck 125 and enter into process chamber 190 via showerhead 140,where the combined gas is applied uniformly to the process chamber 190.Once inside process chamber 190, electrodes driven by a radio-frequency(RF) source (not shown) excite the combined gases. The electrodes andsource, in combination, generate a discharge between the electrodes toionize reactive gases therein. These ionized gases form a plasma thatdeposits film onto, or etches film off of, the substrate in contact withthe plasma. Successive exposures to differing plasmas create desirablesemiconductor films on the substrate. Similarly, coatings or films canbe selectively removed if exposed to plasmas formed by appropriate etchgases (e.g., carbon tetrafluoride).

FIG. 2 shows a second gas temperature-control embodiment 200 thatincludes a neck 125, process chamber 190, chamber wall 150, showerhead140, chuck 160, bellows 180, and pump port 170, as in FIG. 1, and arenot further described. However, the single T/C 130 has been replaced bydedicated species temperature controllers (T/C 210 ₁ through T/C 210_(n)) for each of the gas lines 110 ₁ through 110 _(n). T/C 210 ₁through 210 _(n) are temperature controllers that separately control thetemperature of individual gases, and are explained in further detail inFIGS. 5 and 6.

In operation, for each i in 1≦i≦n, gas 120 _(i) enters its correspondinggas line 110 _(i) and passes through T/C 210 _(i), which heats gas 120_(i) to a predetermined temperature T_(i). The species of gases continuethrough their respective gas lines, combine at neck 125, and proceedfurther to process chamber 190.

FIG. 3 shows a third gas temperature-control embodiment 300 that, likeFIG. 1, includes gas lines 110 ₁ through 110 _(n), neck 125, processchamber 190, chamber wall 150, shower head 140, chuck 160, bellows 180,and pump port 170. Embodiment 300 further includes spatial temperaturecontrollers 310 ₁ through 310 _(m) that alter the temperatures of mixedgas species prior to the introduction of the mixed gas species into theprocess chamber 190. (The number, m, of temperature controllers, neednot equal the number of lines, n, (i.e., n≠m), but they may be madeequal (i.e., n=m).) Each T/C 310 _(i) includes a corresponding inlet 330_(i) and connects neck 125 with differing spatial regions of showerhead140.

In operation, each gas 120 _(i) flows through gas line 110 _(i) and intoneck 125. Within neck 125, gases 120, through 120 _(n) combine to form aprocess gas mixture. The process gas mixture flows through inlets 330 ₁through 330 _(n) and, correspondingly, into T/C 310 ₁ through T/C 310_(m) where each T/C 310 ₁ heats a portion of the process gas to apredetermined temperature. Upon passing through T/C 310 ₁ through T/C310 _(m) the heated process gas flows through the different spatialareas on showerhead 140. In the illustrated embodiment, showerhead 140is divided into a plurality of isolated areas and the temperature ofmixed gas species is controlled for each of the plurality of isolatedareas of showerhead 140.

FIG. 4 shows a fourth gas temperature-control embodiment that, like FIG.1, includes gas lines 110 ₁ through 110 _(n), neck 125, process chamber190, chamber wall 150, shower head 140, chuck 160, bellows 180, and pumpport 170. FIG. 4 also includes the species temperature controllers 210 ₁through 210 _(n) and the spatial temperature controllers 310 ₁ through310 _(m), thereby forming a hierarchy of temperature controllers.

In operation, the temperature of each gas is first controlledindividually with a temperature controller located along each individualgas line. Subsequently, the temperature of the mixed gas species iscontrolled at different spatial areas on showerhead 140. As would beunderstood by one of ordinary skill in the art, multiple individualspecies temperature controllers (e.g., T/C 210 _(i) and T/C 210 _(i+1))can be combined into a larger T/C 210′ without a loss of generality.Similarly, multiple temperature controllers (e.g., T/C 310 _(i) andT/C310 _(i+1)) can be combined without a loss of generality.

FIG. 5 shows gas temperature controller 500 that includes inlet pipe 505_(i), outlet pipe 505 _(o), in-line heat exchanger assembly 510, heater585, cooler 588, and control unit 590. In-line heat exchanger assemblyincludes heat conductor 515 (e.g., a metal conductor), gasthrough-channel 520, heating element 530, cooling element 535, inletside O-ring 540 _(i), outlet side O-ring 540 _(o), membrane support 550,inlet side insulation 560 _(i), outlet side insulation 560 _(o), inletside temperature sensor 570 _(i), outlet side temperature sensor 570_(o), and thermal transfer membrane 580.

Pipe 505 _(i) and pipe 505 _(o) are pipes (e.g., stainless steel pipes)for passing incoming and outgoing gases, respectively, of the gastemperature controller 500.

Control unit 590 comprises a computer controller with memory to storeprocess instructions and interface for coupling to a higher levelcontroller such as a process controller. One example of controller 590is a Model # SBC2486DX PC/104 Embeddable Computer Board commerciallyavailable from Micro/sys, Inc., 3730 Park Place, Glendale, Calif. 91020.

A first embodiment for heater 585 is an electrical resistance heaterwherein heating element 530 comprises a helical coil (or strip)fabricated from a material of high resistivity. Such resistance heatershave typically employed heating elements of a nickel-chromium alloy(nichrome) or an aluminum-iron alloy, which are electrically resistiveand which generate heat when an electrical current is applied throughthe elements. Examples of commercially available materials commonly usedto fabricate resistive heating elements employed in ovens are Kanthal,Nikrothal and Alkrothal, which are registered trademark names for metalalloys produced by Kanthal Corporation of Bethel, Conn. The Kanthalfamily includes ferritic alloys (FeCrAl) and the Nikrothal familyincludes austenitic alloys (NiCr, NiCrFe). Additional materials includetungsten or platinum. Furthermore, heater unit 585 can comprise a DC orAC power supply capable of delivering a current to the resistive heaterelement 530. An exemplary heater power supply is a switch-modeprogrammable DC power supply such as the SPS series commerciallyavailable from American Reliance, Inc. (11801 Goldring Road, Arcadia,Calif. 91006). DC power supplies can be ganged in parallel or series inorder to increase current and/or voltage, and power delivered to theheating element 530. Heater 585 can be controlled through instructionssent from controller 590.

A first embodiment for cooler 588 is a forced convection coolant loopwherein cooling element 535 comprises a helical tube or channel throughwhich a coolant fluid of prescribed temperature and flow rate passes.The coolant can be cooled (or heated) water, ethylene glycol, liquidnitrogen, etc. Through commands sent by the controller 590, cooler 588adjusts the coolant temperature and/or flow rate.

In-line heat exchanger assembly 510 is an actively controlledheater/cooler that has heating and cooling elements described in detailbelow and configured to heat or cool a gas passing through in-line heatexchanger assembly 510. In-line heat exchanger assembly 510 is designedwith various lengths, with longer in-line heat exchanger assemblies 510capable of achieving a larger change in gas temperature due to a greaterheat transfer surface area contained therein and explained below. Atypical length for the in-line heat exchanger can be from 10 cm toseveral meters for current applications.

Gas through-channel 520 is the cavity within in-line heat exchangerassembly 510 through which and around which gas passes as it is heatedor cooled.

Heat conductor 515 (e.g., made of metal such as stainless steel, copper,aluminum) is formed with a corrugated interior surface, thus increasingthe surface “wetted” area that passing gas comes in contact with whiletraversing gas through-channel 520 and maximizing heat transfer to andfrom the gas. The gas is heated by heating element 530 or cooled bycooling element 535 in accordance with process recipe instructionsstored in the memory in control unit 590. A thermal exchange of energyoccurs, via conduction and convection, within and around gasthrough-channel 520 between the passing gas and heat conductor 515,membrane supports 550, and thermal transfer membrane 580.

Inlet side O-ring 540 _(i) provides a seal between inlet pipe 505 _(i)and in-line heat exchanger 510. Likewise, outlet side O-ring 540 _(o)provides a seal between outlet pipe 505 _(o) and in-line heat exchanger510. O-rings 540 _(i) and 540 _(o) further allow thermal contraction ofthe elements of the in-line heat exchanger 510, including heat conductor515.

Membrane support 550 is made of a metal (e.g., stainless steel, copper,or aluminum), supports the thermal transfer membrane 580, and provides amedium of heat conduction between heat conductor 515 and thermaltransfer membrane 580.

Inlet and outlet side insulation 560 _(i) and 560 _(o) (e.g., quartz)serve to prevent thermal conduction to elements outside the in-line heatexchanger assembly 510. The inlet-side insulator 560 _(i) can have aconically divergent gas flow-through section to act as a diffuser (flowdecelerating device), and the outlet side insulator 560 _(o) can have aconically convergent gas flow-through section to act as a nozzle (flowaccelerating device).

Mid-section insulation 565 (e.g., quartz) serves to prevent heattransfer between heat conductor 515 and the environment surrounding thein-line heat exchanger 510. The fabrication of insulators 560 _(i), 565and 560 _(o) from quartz serves to assemble a casing for the in-lineheating/cooling device with low thermal conductivity and smallcoefficient of thermal expansion, but other insulating materials mayalso be used. The heat conducting structure 515 can be fabricated toreside within insulating structures with sufficient clearance toaccommodate differing coefficients of thermal expansion.

Inlet-side and outlet-side temperature sensors 570 _(i) and 570 _(o),respectively, sense gas temperatures and provide feedback to controlunit 590. Inlet-side temperature sensor 570 _(i) is located within gasline section 505 _(i) for the purpose of sensing the temperature ofincoming gas. Outlet-side temperature sensor 570 _(o) is located withingas line 505 _(o) for the purpose of sensing the temperature of outgoinggas. In an alternative embodiment, temperature is sensed in upstream anddownstream regions of in-line heat exchanger assembly, which isinsulated from conducting structure 515. In one embodiment, temperaturesensors 570 _(i) and 570 _(o) are K-type thermocouples.

Thermal transfer membrane 580 is a corrugated membrane (e.g., stainlesssteel, copper or aluminum) and improves thermal transfer between the gasspecies and the heat conductor 515 by exposing the gas to a large heattransfer surface area. Moreover, the thermal transfer membrane 580 canbe formed by an array of concentric (tubular) fins held fixed by themembrane supports 550 and extending the length of the in-line gas heatexchanger 510. In general, surfaces of thermal transfer membrane 580,membrane support 550, and heat conductor 515 can be coated with aprotective coating to minimize gas contamination at elevatedtemperatures. For example, materials can be embedded within quartz,spray coated or anodized.

One embodiment of heating element 530 is a helically wound resistiveheating element that provides thermal energy to heat conductor 515 inproportion to the amount of power supplied to heating element 530 byheater 585.

One embodiment of cooling element 535 is a helically wound elementcontrolled by controller 590, through which a coolant gas or liquidpasses. Heating element 530 and cooling element 535 together form adouble helix.

The elements of temperature controller 500 are interrelated as follows.Control unit 590 is in communication with temperature sensors 570 _(i)and 570 _(o), heater 585 and cooler 588. Heater 585 is in communicationwith heating element 530, and cooler 588 is in communication withcooling element 535. In-line heat exchanger assembly 510 is disposedbetween pipes 505 _(i) and 505 _(o). Insulation 560 _(i), 565 andinsulation 560 _(o) encase the inner elements of in line heat exchangerassembly 510, including heat conductor 515, O-rings 540 _(i) and 540_(o), and gas lines 505 _(i) and 505 _(o). Heat conductor 515 encasesheating element 530, cooling element 535, and temperature sensors 570_(i) and 570 _(o). Heat conductor 515 is in thermal contact withmembrane support 550, which is in thermal contact with thermal transfermembrane 580. Membrane support 550 and heat transfer membrane form a gasthrough-channel 520.

In operation, gas enters temperature controller 500 through gas line 505_(i) and passes through temperature controller 500 along and around gasthrough-channel 520. Temperature sensors 570 _(i) and 570 _(o) arelocated within heat conductor 515 such that temperature sensor 570 _(i)is capable of sensing the temperature of incoming gas species andtemperature controller 570 _(o) is capable of sensing the temperature ofoutgoing gas species. Temperature sensors 570 _(i) and 570 _(o) relaythis temperature information to control unit 590 (periodically,continually, or when polled). Control unit 590 senses the temperature ofin-line heat exchanger 510 and compares the measured temperature withthe desired temperature in the process recipe stored in the memory incontrol unit 590. Control unit 590 then communicates with heater 585 orcooler 588, which activate heating element 530 or cooling element 535 inaccordance with the process recipe. Conductive heat transfer occursbetween heating element 530 and heat conductor 515.Conductive-convective heat transfer occurs between cooling element 535and heat conductor 515. A transfer of thermal energy occurs, viaconduction, between heat conductor 515 and membrane supports 550 andthermal transfer membrane 580. In conjunction with a known gas mass flowrate (via a mass flow rate controller upstream of the in-line heatexchanger assembly 510) and known species composition, the heattransferred to or from the gas can be computed as a function of powerdelivered to heating element 530 or flow rate and temperature of coolantin cooling element 535. Membrane supports 550 and thermal transfermembrane are designed with a large “wetted surface area” (the “wettedsurface area” is the total surface area in contact with the gas; e.g. amomentum and thermal boundary layer exists at these surfaces throughwhich thermal energy is transported) as described above. Gas passingthrough gas through-channel 520 comes in thermal contact with thesurfaces of thermal transfer membrane 580 and membrane supports 550 anda transfer of thermal energy occurs via conduction and convection.

In-line heat exchanger 510 is designed with an application-specificlength that ranges between 10 cm and several meters. For example, anin-line heat exchanger 510 of total length 22 cm and inner diameter of 4cm would be suitable for heating gas from 300K to 800K (or the structuretemperature). An exemplary in-line heat exchanger (low-density gasheater/cooler) 510 includes three sections, namely, an inlet diffuser oflength 6 cm, a gas heating/cooling section of length 10 cm and an exitnozzle section of length 6 cm. The inlet diffuser is a conicallydivergent duct section (preferably having a half-angle not to exceed 18degrees) utilized to increase the flow-through cross-sectional areawithout flow separation. A diffuser length of 5.42 cm (or 6 cm) issufficiently long (per the specification above) to increase the innerpipe diameter from 0.476 cm ({fraction (3/16)} inch inner diameter istypical for gas line plumbing) to 4 cm. If the diffuser half-angle isless than 18 degrees, then the flow will remain attached to the walls;however, if the angle exceeds 18 degrees, it is possible that the gasflow will separate from the walls in the diffuser and reduce gasheating/cooling efficiency. The diffuser serves the primary purpose ofslowing the gas flow and expanding the flow cross-section so that theamount of “wetted” surface area within the in-line heat exchanger 510can be substantially increased. In addition to increasing the surfacearea of the inner wall of the gas heating/cooling pipe, the spaceavailable for inserting an array of heat transfer fins is alsoincreased. For example, the heat transfer fins (thermal membrane 580)can be composed of an array of concentric (tubular) fins of radialspacing r or a honeycomb structure of through-hole cross-section d_(h).

For a gas flow rate of 500 sccm (argon) and a typical gas injectiondesign for a plasma processing device, the gas pressure will beapproximately 10 Torr (to first order) at the entrance to the in-linegas heat exchanger 510. At these reduced pressures, the gas flow can betreated as a (viscous) continuum flow when the Knudsen number is lessthan 0.01. At a pressure of 10 Torr, the mean free path is approximately0.005 mm and, therefore, radial fin spacings r or honeycomb through-holediameters d_(h) greater than 0.5 mm (for example) would allow design ofthe in-line gas heat exchanger 510 unit using continuum flow principles(which is preferred since the heat transfer coefficient decreasessignificantly when the Knudsen number increases above approximately0.01; i.e. the mean free path is becoming large relative to the flowstructure). For example, an in-line gas heat exchanger 510 of length 10cm and diameter 4 cm provides sufficient space to insert approximatelynineteen (19) concentric, tubular fins spaced by r˜0.5 mm (given afinite thickness for the fins) such that a total “wetted” surface areaof 0.25 m² is achieved. Given this amount of “wetted” surface area and alaminar flow assumption, the heat transfer will be sufficiently greatthat the gas temperature will reach the structure temperature prior tothe exit of the in-line gas heat exchanger 510. Therefore, the gas exittemperature will assume the temperature of the thermal transfermembrane(s). The thermal transfer membrane structure 580 should befabricated as a low thermal inertia structure from a material of highthermal conductivity as described above. In summary, the exit gastemperature will be limited by the temperature constraints of thematerials comprising the in-line gas heat exchanger 510. Incorporatinglonger in-line heat exchangers 510 allows a greater maximum heatexchange due to an increase in heat transfer surface area in contactwith the passing gas, namely thermal transfer membrane 580, membranesupport 550, and, to a lesser degree, heat conductor 515. Lastly, thelength of the conically convergent (nozzle) section can be less thanthat of the diffuser section. The nozzle reduces the flow-throughcross-section to the inner diameter of the gas plumbing 505 _(o).

In an alternate embodiment, a series of heat conducting screens orbaffle plates can replace the thermal transfer membrane and the membranesupports. In addition, a different number of channels can be used and/ora different number of temperature sensors can be used. Also, the O-ringscan be replaced with another sealing mechanism or they can beeliminated.

FIG. 6 shows an exemplary cross sectional view of a gas temperaturecontroller 500, and includes gas through-channel 520, insulation 565,heat-conducting metal 515, membrane support 550, and a single thermaltransfer membrane 580. As described above, additional fins can berequired.

In operation, the dimensions of gas through-channel 520, heat-conductor515, and membrane supports 550 are designed such that the volume of thegas through-channel yields the same impedance to the flow of gas as thatof the gas line into which the temperature controller is disposed. Aswould be apparent to one of ordinary skill, the number of concentricchannels can be varied to carry different gases or the same gas.Moreover, insulators may thermally isolate the heat transfer to onechannel from another channel in an alternate embodiment.

In yet another alternate embodiment, the heat exchanger is not a linearheat exchanger but a serpentine exchanger wherein the gas flows back andforth while being heated or cooled. This enables heat exchange over ashorter linear distance for compact form factors or designs.

FIG. 7 shows a method of controlling the temperature of gas speciesflowing through at least one in-line heat exchanger assembly of atemperature controller. Procedure 700 starts in step 705 by selecting aprocess type and initiating the flow of a process gas according to theprocess type.

In step 710, control unit 590 senses the temperature of in-line heatexchanger 510 communicated by temperature sensors 570 _(i) and 570 _(o).

In step 720, control unit 590 compares the measured temperature with thedesired temperature in the process recipe stored in the memory incontrol unit 590. If the results of the comparison indicate that atemperature adjustment is required, then control passes to step 730;otherwise, control passes to step 740. Control unit 590 sends comparisondata to a process controller (not shown). In addition, control unit 590determines if the temperature adjustment can be made and reports theresults to the process controller. In a preferred embodiment, gastemperatures operate within ranges established for each process. Controlunit 590 receives temperature range data from a process controller. Instep 730, control unit 590 instructs heater 585 to provide power toheating element 530 or control unit 590 instructs cooler 588 to supply aflow of cooling gas or liquid through cooling element 535.

In step 740, control unit 590 determines if the process is complete. Ifthe process is complete, controller 590 communicates to heater 585 andcooler 588 to cease operation and procedure 700 ends at step 750. If theprocess is not complete, procedure 700 branches to step 710, andcontinues as shown in FIG. 7.

Numerous modifications and variations of the present invention arepossible in light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described herein.

1-13. (Canceled).
 14. A method for operating a temperature controllercoupled to a process chamber, the method comprising: determining aprocess type; supplying a process gas to the process chamber through anin-line heat exchange assembly, the process gas being determined fromthe process type; determining a desired gas temperature for the processgas using the process type; determining gas temperature in the in-lineheat exchange assembly; comparing the gas temperature to the desired gastemperature using a control unit coupled to the in-line heat exchangeassembly; and adjusting the gas temperature in the in-line heat exchangeassembly when the comparison indicates that a temperature adjustment isrequired.
 15. The method for operating a temperature controller coupledto a process chamber according to claim 14, the method furthercomprising: supplying a second process gas to the process chamberthrough the in-line heat exchange assembly, the second process gas beingdetermined from the process type; determining a desired gas temperaturefor the process gasses using the process type; determining gastemperature for the process gasses in the in-line heat exchangeassembly; comparing the gas temperature for the process gasses to thedesired gas temperature for the process gasses using a control unitcoupled to the in-line heat exchange assembly; and adjusting the gastemperature for the process gasses in the in-line heat exchange assemblywhen the comparison indicates that a temperature adjustment is required.16. The method for operating a temperature controller coupled to aprocess chamber according to claim 14, the method further comprising:supplying a second process gas to the process chamber through a secondin-line heat exchange assembly, the second process gas being determinedfrom the process type; determining a desired gas temperature for thesecond gas using the process type; determining gas temperature for thesecond gas in the second in-line heat exchange assembly; comparing thegas temperature for the second gas to the desired gas temperature forthe second gas using a control unit coupled to the in-line heat exchangeassembly; and adjusting the gas temperature for the second gas in thesecond in-line heat exchange assembly when the comparison indicates thata temperature adjustment is required.